From Refugio Elola walk up to Hoya de Antón following a signed path and go through this plain pointing to the left (South), towards Portilla Bermeja.
After a steep first section, reach a little plain where the slopes of Portilla Bermeja and Portilla del Crampón join. Go up along the slope to the right (west), wich progressively is narrower and steeper (45º - 50º). Once on Portilla del Crampón cross up the SW face (caution in winter) and climb the last meters directly to the right or to the left of some prominet rocks.
It´s the most frecuented route because of its difficult and distance from Refugio Elola. In winter the upper part until Portilla (gap) del Crampón have a steep slope and require to take precautions. Crampons and ice axe are necessary from November to May. Also harness, a rope and some ice bolts could be indispensable.